Warren is the ghost of the Phoenix House.  Killed thousands of years ago when his homeland "blew up real good," Warren seems to have no real connection to Shaldani other than the fact that he enjoys frequenting the Phoenix House.  In his life, Warren was an artist and boasted of having more lovers than anyone else in his village.  After his death, Warren spent many years observing humanity.  While in his life he was a free spirit who believed in goodness and freedom, in his death he grew cynical, even a bit bitter.  When the Ebene magic shield over Shaldani made it impossible for Warren to communicate with the living, he was prepared to return to the spiritscape, but a fortunate turn of events made it possible for Adriana to see ghosts despite the shield.  Warren was somewhat intrigued by her and decided to hang around the Phoenix House.  For now.